The present invention relates to a thermal bag which belongs to the fields of cold chain logistics, product preservation, heat retaining, constant-temperature preservation and so forth
There are two types of thermal bags, namely hard thermal bags and soft thermal bags. A soft thermal bag generally comprises a bag body and a bag cover which are movably connected. The bag body comprises an inner bag, an outer bag and a thermal layer. The inner bag has a top opening and a receiving cavity with certain capacity. The outer bag has a top opening and a receiving cavity which is bigger than that of the inner bag. The thermal layer is disposed between the inner bag and the outer bag for heat isolation and thermal purposes between the inner bag and the outer bag. The thermal layer has a front side wall, a rear side wall, a left side wall, a right side wall and a lower side wall which are integrally connected. The bag cover comprises an upper cover, a lower cover and a thermal material layer. The outer side walls of the upper cover and the lower cover are fixedly connected. The thermal material layer of the bag cover is disposed between the upper cover and the lower cover. The bag body and the bag cover are removably connected by zipper or fastening means. Such soft thermal bags may be waterproof or non-waterproof. The parts of a non-waterproof thermal bag are generally connected by sewing; the thermal bag as a whole is more regular in shape and it is more convenient to manufacture, but it has the disadvantage of being non-waterproof. For waterproof thermal bags, the parts are required to be welded by high frequency waves. As illustrated in FIG. 1, during welding of the outer bag 1′ and the inner bag 2′ of the bag body, as the thermal layer 3′ has a certain thickness, it is not possible to weld close to the thermal layer, so that welding has to be performed at a certain distance L from an upper surface of the thermal layer. When the bag cover 5′ covers the bag body, as the zipper 4′ and the portion under the distance L both have poor load bearing strength, the bag body as a whole is not regular in shape; besides, as the portion under the distance L does not have any thermal capacity, heat exchange between the zipper 4′ and the portion under the distance L is greatly increased, thus significantly limiting the thermal effect. Therefore, it is necessary to further improve the thermal effect of existing thermal bags.
The technical problem of existing thermal bags is poor thermal effect.